Lastly, the reptiles, in this age of their imperial sway, culminated in the _Dinosaurians_, animals far above any modern Reptilia in the perfection of their organisation, and many of them of gigantic size. Just as the Pterosaurs filled the place now occupied by the birds, so the Dinosaurs filled that represented by the mammals, or rather they took up a place holding some close relations with both the birds and the mammals. There were thus reptilian animals which on the one hand were the elephants and lions of their time, and on the other bore a grotesque resemblance to creatures so unlike these as the Ostriches, in so far as their anatomical structure was concerned; while it is evident that their whole organisation places them in the highest position possible within the reptilian class. Some of them must have been herbivorous, and probably slow in movement and quiet in nature. Others were carnivorous and of terrible energy, while furnished with the most destructive weapons (Figs. 152, 153). Many had the power of erecting themselves on their hind-feet and walking as bipeds; and to adapt them to this end their hinder limbs were very large and strong, and they had long pillar-like tails, while their fore-feet were comparatively small, and used perhaps mainly for prehension (Figs. 151, 154). [Illustration: FIG. 152.—Jaws of _Megalosaurus_.—After Phillips. One-tenth natural size.] The size of some of these creatures was stupendous. The _Hadrosaurus_ of New Jersey, an Herbivorous species (Fig. 151), when erected on its hind limbs and tail, must have stood more than twenty feet in height. _Megalosaurus_ and _Iguanodon_, of the English Jurassic and Wealden, must have been of still more gigantic size. The former was a carnivorous animal, its head (Fig. 152) four or five feet in length, armed with teeth, sabre-shaped, sharp and crenate on the edges (Fig. 153), its hind limbs of enormous power, so that if our imagination does not fail us in the attempt to realise such a wonder, we may even suppose this huge animal, much larger than the largest elephant, springing like a tiger on its prey, a miracle of terrible strength and ferocity, before which no living thing could stand. Its companion, _Iguanodon_, was, on the contrary, a harmless herbivorous creature, using its great strength and stature as a means of obtaining leaves and fruits for food, and perhaps falling a prey to the larger Carnivorous Dinosaurs its contemporaries. A still more bulky animal was the _Ceteosaurus_, so admirably described by Phillips. Its thigh-bone measures more than five feet in length and a foot in diameter; and it must have stood ten feet high when on all fours, while its length must have reached forty or fifty feet. It seems from the forms of its bones to have been able to walk on land, but probably spent most of its time in the water, where it may be compared to a huge reptilian hippopotamus. Very recently some bones found in